In the Long Term Evolution (LTE for short) system and LTE-Advanced (LTE-A for short) system, control signaling of the downlink physical layer contains downlink transmission related downlink grant (DL grant) information which needs to be known by the terminal and uplink transmission related uplink grant (UL grant) information which needs to be known by the UE, and such control signaling of the physical layer is transmitted on the Physical Downlink Control Channel (PDCCH for short).
In the Release (R for short) 8/9 of the LTE system and R10 of the LTE-A system, the PDCCH for transmitting the control signaling of the physical layer is generally configured to be transmitted on first N Orthogonal Frequency Division Multiplexing (OFDM) symbols, which are referred to as a control signaling transmission area. In the present document, in order to be distinguished from the newly added control signaling transmission area of the new release, the control signaling transmission area of the R8/9/10 is referred to as a first control signaling transmission area.
Available transmission resources in the first Control signaling transmission area are divided into multiple resource units of Control Channel Elements (CCEs), the occupied resources of the control information are allocated with the CCE being a unit, and the resource unit of CCE here can also be further subdivided into multiple Resource Element Groups (REGs), wherein, one CCE is comprised of multiple discontinuous REGs, and in general, 9 REGs constitute one CCE, and each REG is comprised of multiple basic resource units.
It can be seen that the control signaling transmission resources allocated by a user are not continuous, which brings a lot difficulties in implementing the closed-loop precoding technique in the multi-antenna system, such that the control signaling area can only use the diversity technology, and it is difficult for it to use the closed-loop precoding technique. The primary reason is that there is a great design difficulty in the design of the demodulation pilot and the feedback of the channel state information for the first precoding area, and therefore, all the control signaling in the existing releases only supports discontinuous resource transmission and diversity technologies.
In the releases after R10, in order to enhance the transmission capacity of the control channel and support control signaling of more users, the design considers to open up a new control channel area, and control signaling transmission resources of the same UE can be continuous time-frequency resources, to support the dedicated demodulation pilot based single-layer transmission technology (i.e., the closed-loop precoding technology), thus improving the transmission performance of the control information.
The new and old releases of the control signaling area are as shown in FIG. 1. For the new release of the control signaling, a part of transmission resources are set aside from the PDSCH transmission area of the original R8/9/10 to be used as the second control signaling transmission area, which can support the closed-loop precoding technology when the control signaling is transmitted, thus enhancing control signaling capacity and supporting control signaling of more users.
Here, in the second control signaling transmission area, the dedicated demodulation pilot (DMRS) in the R10 can be reused to demodulate the control signaling, which well supports the precoding technique. In addition, for the second control signal transmission area, RB is taken as the unit, which can well perform interference coordination.
At the same time, considering the robustness of the transmission and the condition that there is no channel information, in the second control signaling transmission area, DMRS can also support the open-loop diversity technology, such as SFBC technology.
In order to better understand the background of the present document, the resource definition of the LTE-A will be introduced simply as below: one Resource Element (RE for short) of the LTE is a sub-carrier on one OFDM symbol, while a downlink physical Resource Block (RB for short) is comprised of 12 continuous sub-carriers and continuous 14 (which is 12 when the extended cyclic prefix is used) OFDM symbols, which is 180 kHz in the frequency domain and a time length of one general slot in the time domain, as shown in FIG. 2 (a 5M system). The LTE/LTE-A system performs allocation with a resource block being a basic unit when the resources are allocated.
The second control signaling transmission area mentioned above can support the closed-loop precoding technique and the open-loop diversity technology, and in the related art, the transmission areas of such two transmission technologies as the precoding technique and the diversity technology are transmitted in different RBs respectively, because the diversity technology requires the DMRS not to be precoded and requires multiple UEs to share pilots, while the closed-loop precoding does not allow sharing pilot ports and needs to perform different precodings on different pilot ports and different UEs according to channel information of various UEs.
An example of existing technology is that available transmission resources (RBC-1) in the second control area of RB1 use closed-loop precoding, and multiplex 4 users, as shown in FIG. 3a or 3b. The second control area resources in the RB are divided into 4 parts, each user occupies one part of resources, and each part of resources corresponds to one pilot port. Ports 7 and 8 share some time-frequency resources, and Ports 9 and 10 share some time-frequency resources. Code division is performed between two ports sharing time-frequency resources, to keep orthogonality.
Available transmission resources (RBC-2) in the second control area of the RB2 use the diversity technology, and RB2 is divided into multiple eREGs, as shown in FIG. 4, each REG contains two REs, resources are allocated to multiple diversity users with the eREG being a unit, and multiple users using transmission diversity technology are multiplexed in the RB.
In conclusion, the following problems exist in the related art: as there may sometimes be few users scheduled in the system, whether it is the diversity or the closed-loop precoding, there may be a condition that the resources in the RB are used insufficiently, the utilization rate of the resources is not high, and the waste of the resources is serious especially for the diversity technology when there are few users.